Machine-switching telephone-exchange system



Jan. 29, 1929. 1,700,466

w. w. CARPENTER MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed March 5. 1921 5, Sheets-Sheet 1 UUDUUD DU M er/for.-

Warren M (WWW/en W. W. CARPENTER MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Jan. 29, 1929.

Filed March 1921' 5 Sheets-Sheet 2 NKET J R T //4 van mn- Warren 14 tame/4m.

Jan. 29, 1929. 1,700,466

W. W. CARPENTER momma SWITCHING TELEPHONE EXCHANGE syswu Filed March 5. 1921 s Sheets-Sheet 5 Jan. 29, 1929.

W. W. CARPENTER MA HINE SWITCHING TELEPHONE EXCHANGE, SYSTEM Filed March 5 1 1 aspects-sheet 4 wwv - wok wm gq //4 van ram K I M M W1. K v R m 2 M4. b

Jan. 29, 1929. 1,700,466

w. w. CARPENTER MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed March 5. 1921 SSheets-Sheet' 5 m ew/0r: h arrw h fame/4 far Patented Jan. 29, 1929.

UNITED STATES PATENT OFFICE.

WARREN w. CARPENTER, or BROOKLYN, NEW YORK, AS1GNOB 'ro WESTERN ELEC- TRIO comm, INCORPORATED, or NEW YORK, N. Y., A CORPORATION on NEW,

YORK.

Application filed March a, 1921. 8er1a1llo.449,812.

This invention relates to machine switching telephone exchange systems.

Its object is to provide an improved system employing what are known as two hundred point switches, and the circuit arrangement is such that the same type of switch serves as a finder, selector or connector.-

In the system of this invention each of the automatic switches has two sets of talking brushes and two test wipers. When a finder reaches the calling line,.having been set in motion by the initiation of the call, the proper brush set is connected to such line, the other set'being left disconnected. The associated first selector is now raised a number of steps corresponding to the first digit whereupon it begins to rotate, testing two trunks at each step, moving on if both are busy and if one is idle seizing it. The succeeding selectors are similarly operated. .The set of connector talking brushes rendered operative is de-' termined by the odd or even character of the digit involved in setting the preceding selector. Inasmuch as a 1ven connector takes care of two hundred lines it is reached over either one of two levels of the preceding selector. In order to render the brush set serving the. desired hundred of the two hundred lines terminating in the connector operat1ve, the test wire from the odd hundreds level in the preceding selector from which the connector may be reached includes a switching relay which operates when the digit involved in setting the said selector is odd and connects the brushes serving the odd hundred to the calling end of the circuit. The test wire from the even hundreds level of the selector from which the same connector is reached does not include this relay, and consequently the other set of brushes is left connected to the calling end of the circuit.

Referring to the drawings, which should be arranged in numerical order beginning from the left, Fig. 1 shows the subscribersline circuits and a finder; Fig. 2 shows a first selector; Fig. 3 shows a second selector; Fig. 4 shows a third selector; Fig. 5 shows a connector.

The invention will be more readily understood from a detailed description of the operation.

Upon the removal of the receiver at-substation X, the line relay 161 operates over the following circuit, free pole of battery, right WHldiniOf relay 161, Inner right armature and bac contact of the cut-off relay 162, line conductor 136 through the substation 100 at X, returning to ground over-the line con notor 187 and outer right-hand armature and back contact of relaz 162. The line relay 161 in attracting its rig t armature operates the group relay 100 over the following path: grounded right armature and front. contact of relay 161, conductor 101, armature and back contact of relay 102, relay 100, free pole of battery. Relay 100,-in attracting its upper armature, locks itself to the grounded right-hand armature .of-line relay 161 and also applies ground to the contact 103 which is common to the group to which substations X and Y belong. In attracting its lower armature, relay 100 operates relay 102 which temporarily removes relay 100 from the control of the other subscribers 109, armature and back contact of rotary magnet 110, relay E, free pole of battery. Belay E in attractin its right armature extends this ground to t e slow relay C and vertical magnet 109 in series, b way of the right normal contact of relay X, whereupon'the vertical magnet steps the finder one step in its vertical movement. Relay E upon energizing locked itself .over the following circuit: free pole ofbattery, relay E, armatures and back contacts of magnets 110 and 109, conductors 108 and 111, inner left armature and front contact of relay E to ground. The vertical magnet 109 at the end of its stroke, opens the locking circuit of relay E. as well as the original energizing circuit of said relay, whereupon the relay E releases and opens over its original energizing circuit,

112 of t whereupon it looks u over its locking circuit, the operation 0 .relayE transmitting another impulse to the vertical magnet 109. This interaction of the relay E and the vertical ma net continues until the grou brush l ae finder reaches the groun ed segment 103. of the calling group, whereupon the relay A operates over the following circuit: free pole of battery, relay E, armature and back contact of'magnet 110, conductor 113, right winding of relay A, conductor 114 to ground on the group segment 103. Relay A at its right armature opens the vertical stepping circuit. At .the moment that the group brush engages this grounded segment, the relay E is still locked up, since its locklng circuit 1s only 0 ened at the extreme limit of the stroke 0 the vertical magnet 109. When this occurs the relay E does not release because it has a circuit including the right winding of relay A to ground on the group segment 103. When the slow relay C releases, which occurs shortly after relay A operates, the following circuit is closed to operate the rotary magnet 110 to rotate the brushes over the calling line group: free pole of battery, magnet 110, armature and ack contact of relay G, right armature and front contact of relay A, conductor 116, right armature and front contact of relay E, armatures and back contacts of magnets 110 and 109, conductors 108, 111, to ground at the inner left armature'and front contact of relay E. Magnet 110 rotates the brushes one step a and at the end of its stroke opens the locking circuit of the relay E and also moves the group brush 112 off the grounded group contact 103. If the first two sets' of terminals encountered by the brushes are terminals of non-calling lines, the brush shifting relay B which was operated when relay A operated at the end of the vertical movement over a circuit including the outer left armatures and front contacts of relays E and A, remains operated overthe following circuit: free pole of battery, relay B, its armature 117 and front contact conductor 118, contact 119 of relay D, conductor 120, 121, brush 122, test multiple 123, conductor 124, left armature and back contact of the cut-off relay 164 and right armature and back contact of line relay 163 of line Y to ground, and armature 125, of the relay B transmits an impulse-over the following circuit to again pull up the relay E to transmit another impulse to the rotary magnet to advance the finder from the terminals of these two lines which are noncalling to the next two lines: free pole of battery, relay E, armatures and back contacts of magnets 110, 109, conductors 108, 111, 131, armature 126 of relay D, conductor 127, armature 125 and front contact of relay B, test brush 130,'test terminal 128 conductor 129, left armature and back contact of the cut-off relay 162 right armature andback contact of the line relay 161 to ground. Relay E in operating again locks up over the circuit heretofore traced, including its inner left armature and front contact and again 0 crates the rotary ma net 110, over the fol owing circuit: grounded test multiple 128, brush 130, armature 125 and front contact of relay B, conductor 127, armature 126 and back contact of relay D conductors 131, 111, 108, armatures and back contacts of the magnet 109, 110, right armature and front contact of relay E, conductor 116 right armature and front contact of relay A, armature and back contact of relay C, magnet 110, free pole of battery. The rotary magnet at the end of its stroke opens the lockin circuit traced for the relay E, which in rdleasing its right armature opens the circuit of the rotary magnet. This interaction of the relay E and the rotary magnet 110 continues unt1l one of the sets of brushes encounters a calling line, which is indicated by the absence of ground at its test terminal. It havin been assumed that the calling line is su station X no ground is present at its terminal 128, but ground is present on test terminal 123 of the non-calling substation Y. Consequently, relay B is held up from the ground on test multiple 123. There being no ground, however, at test terminal 128, relay E cannot again energize to transmit another impulse to the rotary magnet. The switch thus comes to rest on the calling line multiples. During the movement of the finder over the non-calling line terminals, the relay D is not operated since its upper winding is short-circuited over the following path: conductor 131, armature 126 and back contact of relay D, conductor 127, armature 125 and front contact of relay B, brush 130 to grounded test terminals 128 of non-calling lines. When the brush 130 reaches test terminal 128 of the substation X which is calling and therefore is not grounded, relay D energizes over the following circuit: free pole of battery, relay E, armatures and back contacts of magnets 110, 109, conductors 108, 111, upper winding of relay D, conductor 132, off-normal switch 133, now closed, to ground. Relay D in attracting its lowermost armature maintains the relay B energized from the ground on the off-normal switch 133; Relay B will therefore remain energized until release takes place. In attracting its armature 126 relay D applies a direct ground from the off-normal switclr133 to the cut-off relay 162 of the calling line X to operate the same. This circuit is as follows: free pole of battery, relay 162, left winding of relay 161, its left armature and front contact, conductor 129, terminal 128, brush 130, armature 125 and front contact of relay B, conductor 127 armature 126 and front contact of relay D, conductor 132 to ground at the off-normal switch133. The cut-ofi relay 162, in operating deenergizes the line relay 161. Ground is appliedto the test multiples 128 of substation X in the other finders 1n which it appears to render the same non-calling, this ground supphed over the following circuit: ofl" normal switch 133, conductor 132, armature 126 of relay and its front contact, conductor 127, armature 125 and front contact of relay B, brush 130 to multiples 128. This armature in retracting also releases the group relay 100, which in turn, releases group relay 102 to restore the startin circuit to the control of the other lines. he cut-off relay 162-is now looked over its left armature to ground on the off-normal switch 133. When the group relay 100 energized a circuit was closed for the impulse relay IR, Fig. 2 of the first selector as follows: ground,.lower armature and front contact of relay 100,conductor 134, armature 105 and back contact of relay D, conductor 135, contact 136' of relay D, lower talkin conductor, Figs 1 and 2, armature 200 an back contact of relay D Fig. 2, left winding of relay IR, free pole of battery. This circuit is closed at this time in order to give the relay IR plenty of time to operate and prepare the circuits ofthe first selector for receiving the impulses corresponding to the first digit of the wanted number. The circuit is now ready for the receipt of the first set of impulses, the relays Band D being operated to extend the talking conductors 136, 137 ofsubstation X to the impulse relay IR of the first selector over the brushes 149, 146. The armature 138 engages its spring before the contact 136 has opened, thus providing a substitute circuit for the impulse relay IR over the calling line before the original energizing circuit for said relay including the lower armature and front contact of relay 100 is broken.

Assume now that the call had been initiated by substation Y and substation X is non-calling. In that event, ground would be present on the multiple 128 of substation'X and the multiple 123 of substation Y would be ungrounded due to the attraction of the right armature of the line relay 163 of substation Y. The operation would be the same as just traced up to the time the test brushes 130 and 122 reach'the terminals 128 and 123 respectively. No ground being present on the test terminal 123 of line Y, relay B would release when relay E released due to the opening of its locking circuit by the rotary magnet. Re lay B in releasing connects the trunk talking conductors to the brushes 139, 140 and consequently to the talking conductors 141, 142 of substation Y, disconnecting such trunk from the brushes 146, 149. Although in the case assumed, ground is present on the test multiple 128 and the armature 125 of the relay B is attracted when the brush 130 reaches such contact, the relay B releases its armature 125 before this ground isapplied long enough to ture and for t e rotary magnet to energize sufliciently to actuate its pawl to give the find Y er another step. The rela D operates in this brushes 139, 140 and the calling line talking conductors 141, 142.

The armature 105 of the relay D extends the in-start wire 134 to the out-start wire 143 and thence to the next idle finder. The function of the lower winding of the relay D is permit the rela E to again attract its armato prevent the replacement of the receivers by the parties to a connection and the consequent release of the finder from deenergizing the relay D and thus interfering with a circuit extending over the armature 105 to the out-start wire 143, which circuit at this particular time. may be setting the next finder. The lower locking winding of relay D will hold this relay energized as long as ground is present on the start wire 134, which will be until the finder beyond which is being set has reached the calling line.

Although it has taken considerable time to trace the operations which follow upon the removal of the receiver by the party at the sub station, it will be understood that these operations take place in an extremely short interval of time, and that all of these operations have impulse circuit is therefore, as follows: free pole of battery, left winding of relay IR, Fig. 2, armature 200 and back contact of relay D lower talking conductor, Fig. 2, inner armature and back contact of the finder release magnet 194, armature 138 and front contact of relay D' armature 145 and front contact or relay B, brush 146, multiple 147, conductor I36, through the loop at the substation .X, conductor 137, multiple 148, brush 149, arm'ature 150 and front contact of relay B, armature 160 and front contact of relay D, upper armature and back contact of the release magnet, upper talking conductor,-Figs. 1 and 2, armature 201 and back contact of relay D conductor 202, right non inductive winding of relay IR, switch 203 operated on the eleventh rotary step of the selector, secondary winding of the induction coil'204 to ground. This induction coil is provided for the purpose of giving a dial tone to the subscriber to inform relay T over the folIowing circuit: free pole lowing circuit:

of battery, relay T armature and front contact ofrelay IR, conductor 206 to ground at the armature207 and back contact of the relay D Slow relay T holds up over the line circuit interruptions and prepares a c rcuit for relay E Now upon the first retraction of the impulse relay IR as the being rotated by the party at substation X restores to normal, the relay E operates fromground on the armature 207 of relay -D and locks itself over the following c1rcu1t; free pole of battery relay E ,its right armature and front contact, conductor 208, armature and back contact of the vertical magnet 205, conductors 209 and 210, left armature of relay T to ground. The relay E in attracting its left armature sends an impulse to the vertical magnet 205 over the following circuit: free pole of battery, magnet 205, slow relay C left armature and front contact of relay E conductors 211, 209, 210 to ground at the left armature and front contact of relay T The verticalmagnet 205 at the end of its stroke opens the locking circuit. of the relay E which releases. In releasing its left armature, this relay opens the circuit of the magnet 205 which releases. This occurs before the back contact 212 of the-impulse relay IR is again closed, as the finger Wheel interrupts the line circuit the second time. When this interruption occurs and the contact 212is again closed, the same operations take place, the relay E initially energizing from ground at the armature 207, locking itself to ground at its left armature and front contact, transmitting an impulse to the vertical magnet 205 and slow relay C in series, the vertical ma et at the end of its stroke opening the lockmg circuit of the relay E which in releasing again releases the vertical magnet, whereupon the circuit is ready for the next impulse. The

relay C being slow remalns energized during the transmission of the vertical impulses. When this relay energized at the beginning of the impulses it operated relay F over the folfree pole of battery relay F armature and back contact of the rotary magnet 214, off-normal switch 215, conductor 216, armature and front contact of relay C to ground. Relay F in attracting its upper armature locked itself to ground over conductor 210 and the left armature and front contact of slow relay T which holds up after the impulses are transmitted. In attracting its armature 217, relay F operates the brush shiftingrelay B In attracting its armature 218, relay F prepares the circuit of the rotary magnet 214. A short interval after the relay E releases when the vertical magnet interrupts its circuit' on the receipt of the last vertical impulse, the relayC releases,

finger wheel after the selector.

closing the circuit of which thereupon steps the selector brushes 250, 251,228, 249 243, 236' onto the trunk terminals 219, 220, If both of these first two trunks are busy, the switch will move on and test the next two trunks. These trunk grou s it will be understood are equivalent. I one of the trunks is idle, the switch will stop and seize such trunk. Assuming both the trunks first tested are busy, both test multiples 223 and 224 are then grounded. It will be remembered that relay B operated when relay F operated at the beginning of the vertical movement of Relay 1? does not release until the end of the stroke of the rotar magnet 214 and consequently relay B will liold up over its armature 225, contact 226 of relay D conductor 227, test brush 228 to ground on the test multiple 223 before its original energizing circuit is opened by the retraction of armature 217 of the relay F Ground being also present on the test multiple 224 of the other trunk, an impulse is transmitted to again operate relay F to transmit another impulse to the rotary magnet to advance the brushes a step onto the next two trunks. Thecircuit for relay F is as follows: free pole battery, relayF ,armature and back contact of magnet 214, elf-normal switch 215, conductors 216, 229, 230, armature 231 and back contact of relay D conductor 232, armature and back contact of first selector release magnet 233, conductor 234, armature 235 and front contact of relay B test brush 236 to the grounded test terminal 224. The circuit for the rotary magnet 214 includes the armature 218 of the relay F and normal contact of the slow relay C now inert. Assume now, that when the brushes engage the next two trunks, the upper trunk is busy and the lower trunk is idle. In that event, ground is present on the test multitple 223 of the upper trunk and the test multiple 224 of the lower trunk is open. The presence of ground on the test multiple 223 causes the switching relay B to remam operated as before, and due to the absence of ground on the test multiple 224, the relay F is not again energized to step the selector ahead. The absence of ground on test multiple '224 also permits the switching relay D to o erate over the following circuit free pole of attery, relay F armature and back contact of the rotary ma et, ofi-normal switch 215, conductors 216, 229, 237, switch 238, operated on the eleventh rotary step, relay D conductors 239, 240, 241, 242 to ground at the left armature and front contact of the slow relay T Relay F is marginal and does not operate in this circuit. Relay D did not operate.

when the first two trunks were tested and found busy due to the shunt about its winding closed over the conductor 230, armature 231 and back contact of said relay, conductor 232, armature and back contact of the release magthe rotary magnet 214 4 net, conductor 234, armature 235 and its front contact, brush 236 to the ground. The'switching relay D in attracting its armature. 240

closes a substitute circuit for the relay B as follows: free pole of battery relay B armature and front contact of said relay, conductor 241', armature 240, and front contact ofrelay D conductors 239, 240, 241, 242 to 1 cuit. This circuit includes the multiples 221,

222, brushes 242, 243 and armatures 245, 252 of the relay B Bela I R in attracting its armature energizes t e usual first slow relay T of the second selector, which in attract-- 'ing its upper armature grounds the release wire. 300 leading back to the first selector. This ground comes on before the slow relay T at the first selector releases due to its circuit being opened b the release of the impulse relay IR when t e switching relay D disconnects it from the calling line. Therefore, the relay D is held up over the following circuit: free pole of battery, relay F armature and back contact of magnet 214, off-normal switch 215, conductors 216, 229, switch 238, relay D conductors 239, 247, armature 231 and front contact of relay D conductor 232, ar-

mature and back contact of the release magnet 233,conductor 234, armature 235 and front contact of relay B brush 236, multiple 224' to the grounded sleeve wire 300. This ground also causes the seized trunk shown in Fig. 3 to test busy. Assumingon the other hand that the uppe trunk was idle and the lower trunk busy, the test multiple 223 would'be ungrounded, and the test multiple 224 would be grounded.

Due to the absence of ground on test multiple 223, relay B would release when its circuit is opened by the retraction of the armature 217 of relay F and shift the trunk talking conductors 248 and 249 to the upper talking brushes 250, 251. As in the case of the line finder, although ground is present on the test multiple 224 when the brush 236 encounters such terminal, relay B releases before this ground is applied long enough to pull up the relay F and allow the rotary magnet to magnetize sufiiciently to give the selector another step. As soon as the armatures 245 and 252 release, the impulse relay, I R operates over the calling line, energizing slow relay T which supplies ground to the sleeve wire 300 leading back to the test multiple 223 thus providing a substitute circuit for the relay D before the circuit of suchre'lay is opened by the release of the slow relay T, as before. This ground also causes the seized trunk to test busy.

Assuming that the lower trunk is the one seized, the impulse relay, I R8 is now energized over the calling line circuit. The return for the impulse relay includes a noninductive winding of relay 303 for balancing purposes. Upon the restoring movement of the finger wheel after being operated for the second digit, each interruption of the line circuit causes an impulse to be transmitted to the vertical magnet 301 of the second selector to elevate the brushes opposite two equivalent trunk groups, as in the case of the first selector. Thecircuits for operating the second selector are ver similar to those for operating the first se ector. The first retraction of the impulse relay I R o erates relay E corresponding to relay E i 2) over ;the following circuit: ground, hack contact of relay 1, R lower armature and contact of switching relay D conductors- 308, 310, 309, to ground at the upper armature and front contact of relay T Relay E in attracting its lower armature extends this ground to the vertical magnet 301 over the following circuit: upper grounded armature of relay T conductors 309, 310, 311, lower armature and front contact of relay E armature 312 and back contact of relay D slow relay C vertical magnet 301, free pole of battery. The vertical magnet at the end of its-stroke unlocks the relay E which in releasing deenergizes the magnet 301 and the circuit is ready for the next impulse. The slow relay G remains operated during the vertical impulse, similarly to the relay C Relay C upon energizing at the beginning of the impulses operated relay F corresponding to relay F (Fig. 2) over the folerating locks itself over the following circuit: free pole of battery, relay F armature and back contact of the rotary magnet, ofi normal switch 315, conductor 316, armature 318, and front contact of relay F conductors 319, 320, 310, 309 to ground at the upper armature and front contact of slow relay T At the end of the vertical impulses the I retraction of the slow-relay C closes a circuit for the rotary magnet 314 to step the brushes onto the first two trunks. This circuit is as follows: free pole of battery, magnet 314, lower armature and front contact of relay F", normal contact of relay C, conductors 317, 311, 310, 309 to ground at the armature and front contact of relay 'T". At the end of the stroke of the rotary magnet the locking circuit of relay F is opened which-in releasin opens the circuit of the rotary magnet. If these two trunks are busy their test multiple 320, 321 will be grounded which will result in the second selector takin another step. If either of these trunks is id e, that is to say, if either of these test terminals is ungrounded the selector will sto and seize such trunk. Assuming that hot trunks are busy the relay B corresponding to relay B (Fig. 2), which operated when the relay F was energized, the circuit including the armature 322 and front contact of relay F remains operated over the following circuit as the test brush 323 engages the grounded test multiple 320; grounded multiple 320, brush 323, conductor 324, normal contact 325 of relay D conductor 326, armature 327 and front contact of relay B winding of relay B free pole of battery. The ground onthe test multiple of the other, trunk causes the relay F to again operate over the following circuit: grounded multiple 321, test brush 328, armature 329 and front contact of relay B conductor 330, armature and back contact of release magnet 331, conductor 332-, armature 333 and back contact of relay D conductors 334, 316-, ofi-normal switch 315, armature and back contact of rotary magnet 314, relay F free pole of battery. Relay F operates and locks up over the circuit previously described includin the armature and front contact of slow re ay T and in attracting its armature 335 transmits another impulse to the rotary magnet to step the selector to the next pair of trunks which magnet in operating opens the locking circuit of relay F which in releasing opens the circuit of the rotary magnet as previously described.

Assuming however that the upper trunk was busy and. the lower trunk idle. In this event, ground is present on the upper test multiple 320 and the lower test multiple 321 is ungroun-ded. The presence of ground on the upper test multiple maintains the relay 323 energized, and the absence of ground on the lower test multiple prevents the relay F from operating to cause the selector to take another step. Due to the absence of ground on the lower test multiple 321, the switching relay D operates over the following circuit; it having been shunted out when the selector tested the first two trunks, due to the presence of ground on the lower test multiple. The circuit for operating relay D is as follows: free pole of battery, relay F armature and back contact of the rota magnet, switch 315, conductors 316, 334, re ay D conductors 311, 310, 309, upper armature and front contact of relay T to ground. Relay 1) in attracting its armature 337 closes a holding circuit for the relay 13 independent of the ground on the test multiple 320, which may e removed at any time due to the release of this trunk by the selector which seized it. This circuit is as follows free pole of battery, relay B its armature and front contact, conductor 326, armature 337, and front contact of relay D conductors 311, 310 to ground at the upper-armature and front contact of relay T This relay in attracting its other armatures prepares circuits for permitting the third selector to be operated by the impulse relay I R of the second selector, which circuits will be traced.

Assuming on the other hand that the upper trunk was idle and the lower trunk busy. In this event, the test multiple 320 of the upper trunk is ungrounded and the test multiple of the lower trunk is grounded. The absence of ground on the upper test multiple 320 fails to provide a holding circuit for the relay B F by the rotary magnet 314, relay l3 releases. Although ground is present on the test multiple 321 when the brush 328 engages it, relay B releases before this ground is applied long enough to again operate the relay F and the rotary magnet 314 to step the selector another step: Due to the absence of oun and when its original energizing circuit 1s opened due to the release of relay on the test muliple 320, the shunt, be ore referred to, about the switching relay D is opened and this relay energizes over the circuit previously described, including the upper armature and front contact of the slow relay T Under these conditions the calling line is extended by the retraction of the armatures 338 and 339 to the upper talking brushes 340, 341 and thence to the third selector (Fig. 3). When the third selector is seized a circuit including the upper winding of relay D thereat is closed from round on the third wire 413. This winding is arranged to magnetize the relay sufliciently to cause it to attract only its uppermost armature a, the other armatures remaining retracted. The attraction of the uppermost armature interposes a break in the circuit of the third selector release magnet 440. Upon the receipt of the impulses corresponding to the third digit, the impulses relay 1 R vibrates its armature to cause the transmission of impulses to the vertical magnet 400 of the third selector. The first retraction of the armature of the impulse relay I R closed the original energizing circuit previously traced for the relay E The locking circuit for this relay, however, in this case, is as follows: free pole of battery, relay E conductor 305, armature and back contact of the vertical magnet 301, conductor 306, upper armature and front contact of rela 8 armature 307 and front. contact of re ay which is now operated, conductor 342, upper talking conductor, armature 338 and its front contact, assuming the lower trunk to have been seized, talking brush 343,

- vertical magnet 400 over the following circuit:

ground, upper armature and front contact of relay T (Fig. 3), conductors 309, 310,

311, lower armature and front contact of're lay E armature 312 and front contact of relay D now operated, conductor 345, normal contact 346 of relay 303, lower talking conoluctor, armature 339 and front contact of relay B talking brush 347, multiple 348, lower talking conductor, (Fig. 4), armature 403 and back contact of relay D, conductor 404, slow relay C vertical magnet 400, free pole of battery. 'At the end of the stroke of the vertical magnet it opens its contact thus releasing the relay E 3), which in rc tracting its lower armature opens the circuit traced for the vertical magnet 400 whereupon the circuit is in condition for the next cycle of operations which is started when the impulse relay I R again releases due to the second break in the line circuit, caused by the finger wheel at the substation. The operations just traced continue until all the vertical impulses are transmitted, which positions the brushes 417, 418, 406, 420, 414, 411 opposite the de sired level having trunks terminating in con-' nectors upon which terminate the desired line multiples. The relay C is similar to the relay C and C (Figs. 3 and 2) and remains energized during the transmission of the .vertical impulses. When this relay operated it ener ized relay F which corresponds to relaysa and F 2 (Figs. 3 and 2) over the following circuit free pole of battery, relay F, armature and back contact of the rotary magnet 404 of the third selector, olf-normal switch 405, armature and front contact of relay C to ground. Relay F in attracting its inner right armature locks itself up and transmits an impulse to the rotary magnet 404 when the slow relay C releases a short interval after the transmission of the vertical impulses, the circuit for the magnet 404 including the left armature and front contact of the relay F 4 and the normal contact of the slow relay C The set of brushes are now in engagement with the first trunks of equivalent groups and the relay B is operated at this time. Its original energizing circuit was closed when the relay F closed its outer right armature and if both trunks are busy, that is to say, test multiples 457 and 407 grounded,

relay B holds up over the ground on multiple 457 and the ground on multiple 407 again operates relay F to transmit another impulse to the rotary magnet 404 to step the brushes on to thenext two trunks. -The circuit for holding relay B operated leads over its armature 408, normal contact 409 of relay D, test brush 406 to the grounded multiple 457. The circuit for again operating relay F leads over grounded multiple 407, test brush 411, armature 412 and front contact of relay B, con-, ductor 450 armature 460 and back contact of relay D3 conductor 414, switch 405, relay F free pole of battery. Relay F locks up in the circuit previously traced and transmits an impulse to the rotary magnet 404 over the circuit previously traced. If the upper trunk is busy and the lower trunk idle the ground on the uppger trunk test multiple 457 holds the relay 4 energized, and the absence of ground on the test multiple 407 of-the lower trunk causes the relay 4 to remain inert. The absence of ground on the lower trunk removes the shunt from about the switching relay D which now receives enough current through its lower winding to operate over the following circuit: free pole of battery, relay F, armature and back contact of the rotary magnet, switch 405, conductor 414, lower winding of relay D, release conductor 413, test multiple 321, brush 328, armature 329 and its front contact, conductor 330, armature and back contact of release magnet 331, conductor 332, armature 333 and front contact of relay D conductors 320, 310, 309, to ground at the upper armature and front contact of relay T Relay F is marginal and does not operate in this circuit. Relay D in attracting its armature 419 provides a ture 460 applies ground to the test multiples 407 and 436 to cause'the seized trunk to test busy to other switches, as will appear more in detail hereinafter. In attracting its armatures 401, 403, relay D extends the calling to the talking brushes 420, 414 and cuts ofl' the bridge containing the vertical magnet 400. If, on the other hand, the upper trunk was idle and the lower trunk busy, the test brush 406 finding no ground on the test multiple 457 of the upper trunk causes the release of the relay B In this latter event, relay B in releasing its armatures 415, 416 extends the calling line to the upper talking brushes 417, 418. The absence of ground on the'upper test multiple 457 removes the shunt from about the relay D which operates to effect the results described. The attraction of the armature 460 of the relay D grounds the test multiple 406 of the up er trunk to cause the same to test busy to ot er third selectors.

Referring toFigs. 4 and 5, it will now be necessary to explain how the selection of a iven line in a 200 point switch is secured, the impulse sender operating on the decimal basis. Assume the called number to be 24267 and that the selector shown in Fig. 4 is now connected to trunk 422, 423, 406. When the calling line is extended to the connector, Fig. 5 in which the conductors 422, 423 terminate, ground is supplied to the test wire 406, from armature 460 of relay D operates from this ground, w ich in turn causes relay 545 to operate from ground on sleeve wire 406 through armature 519 and front contact of relay 544, conductor 501, olfnormal switch 502 now closed, lower winding of relay 545 to battery. Upon the return of the finger wheel in transmitting the tens digit, each retraction of the armature of the impulse relay I impulse to the relay E as previously described. Relay E in operating, locks up and extends the ground from the upper armature of the relay T to the vertical magnet 505 which at the end of its stroke, breaks the locking circuit of relay E The locking circuit for relay E leads over its upper armature, armature 307 and front contact of relay D conductor 342, the upper talking conductor, Figs. 3, 4 and 5, armature 546 and front contact of relay 544, armature 547 and back contact of relay 548, conductor 549 to ground at the armature and back contact of the vertical magnet 505. The stepping circuit for said magnet leads from ground on wire 311, lower armature of relay E armature 312 and front contact of relay D conductor 345, contact 346 of relay 303, lower talking conductors (Figs. 3, 4, and 5), armature 509 and front contact of relay 544, armature 508 and back 'contact of relay 548, slow relay C ,'armature 503 and front contact of relay 545 to battery through the magnet 505. The connector is thus stepped up the number of steps corresponding to the tens digit involved, which in I the present case, is presumed to be 6. Slow relay C is operated in this circuit and being slow holds up over the breaks in its circuit. In attracting its inner left armature, relay C holds up the relay 545 after th'e'off-normal switch 502 opens on the first step of the connector. At the end of the'impulses, relay C releases, releasing relay 545 which in retracting its armature 503 transfers the impulse circuit to the rotary magnet 504. The restoration of the finger wheel transmits seven impulses and causes the impulse relay I B Fig. 3, to repeat these impulses to the rotary magnet 504, which rotates the brushes into engagement with the line No. 24,267. During the transmission of the rotary impulses, relay C is operated as in the case of the vertical Rela 544, Fig. 5,

B (Fig. 3), transmits an' talking battery to the called line.

impulses, and in attracting its inner left armature o erates relay 550 over a circuit including t e armature 520 and back contact of relay 545 which released on the termination of the tens impulses. Relay 550 looks up to the grounded sleeve wire 406. When re- Groun is now connected through armature.

508 of relay 548, armature 509 of relay 544 over the ring conductors 510, 423, brush 413, armature 416 and front contact of relay B, armature 403 and front contact of relay D, armature 339 and front contact of relay B contact 346, conductor 345, armature 312 an front'contact of relay D, lower armature and back contact of E, lower winding of relay 303, free pole of battery. This ground is removed when slow relay 544 releases which occurs shortly after its locking circuit is opened by the attraction of the armature 512 of relay 548. Off-normal contact 551 is at this time open. Relay 303 in attractin its armature 302 disconnects relay E from file lower front contact of the slow relay T Relay 303 in operating locks up to round on the upper armature of slow relay In attracting its armature 355 it disconnects conductor 345 from the lower talking conductor. In attracting its armature 356 it disconnects its upper winding from the uper talking conductor, and in attracting its armatures 357 and 355 it prepares a circuit for supplying Relay 545 is connected to the'sleeve conductor of the called line over brush.514, armature 515 of relay B and its back contact, conductor 516, right arm ture and back contact of relay 0, conductor 517, upper winding of relay 545,

conductors 518, 501, armature 519 and front contact of relay 544 which is still operated at this time to the grounded sleeve wire, causing relay 545 to operate from full potential through the cut-off relay 552 in case the called line is not busy. Relay 545 then locks through its armature 520 and its front contact to ground on the sleeve wire 406. The attraction of armature 542 of relay 545 applies a direct ground from the armature 525 and backcontact of relay 544 to the test multiple 526 to cause the seized line to test busy. The circuit of relay 548 is opened by the operation of relay 545 at the back contact of armature 520. Relay 548 in releasing connects ringing current from the generator 521 to the called line, ground return being supplied over the armature 522 of the ringing cut-off relay 553. When the called party answers, relay 553 is operated and locks over its lower winding and armature 523 to ground on the sleeve wire 406 and connects the talking circuit through.

Upon the operation of the relay 553 and the ated it is connected to the corresponding line extension of the calling line to the called line, the called line battery feed relay 360 operates over the called line, and reverses the current flow in the calling line, which reversal may be used for metering. The subscribers may now converse, talking current being fed to the calling line over relay I R and to the called line over the relay 360, the calling and called lines being separated by the usual condensers, 350, 351. 7

Assuming now that the line desired had been busy. In this event, due to the ground on the multiple 526, the upper winding of the relay 545 is shunted, and this relay fails to operate. Due to the non-operation of relay 545 relay 553 applies busy tone to the calling subscriber from the busy tone source 527, armature 528 and back contact of relay 553, conductor 529, armature 530 and front contact of relay 548 to the tip conductor 530 and thence to the calling line. Rela 548 is at this time operated due to the fallure of the test relay 545 to operate.

Assuming now that the hundreds digit of the desired number had been odd instead of even, that is to say, assuming it to be 24,167

instead of 24, 267. In that event, the selector, Fig. 4, would have been elevated one step opposite the level shown in the lower portion of the sheet, Fig. 4, and would have seized one of these trunks. When either of the trunks 422, 423, or 441, 442 is seized, the ground on the sleeve wire from the armature 460 of relay D is connected directly to battery through the relay 544 of the connector (Fig.- 5). In case the trunk 441,442 had been seized instead of 422, 423 as described, the ground on armature 460 wouldhave been transmitted to the sleeve wire 443 of trunk 441, 442 instead of sleeve wire 406. On the other hand if either of the trunks 431, 432 or 433, 434 is seized, ground is applied to-the correspond ing test wires 435, 436 and'the circuit leads through the lower winding of relay B (Fig. 5), before passing to battery through the winding of relay 544. Relay B when operated locks directly to the grounded sleeve '436. Therefore, when either of the trunks 431, 432 or 433, 434 is seized, which will be when the hundreds digit is odd, the brush shifting relay B operates and transfers the incoming talking conductors of the connector to the brushes 531, 532 which serve the odd hundred lines in the connector, the other brushes 534, 535, serving the even hundreds, being disconnected from the trunk. The test brush 526 serving the even hundreds is also disconnected from the test wire 516 and the test brush 554 serving the odd hundreds is substituted. After the setting of the connector therefor, if the relay B is operated, the calling line is connected to a line in the odd hundreds, whereas if the relay is operswitch to normal.

in the even hundreds.

Upon the conclusion of the conversation and the replacement of the receiver by the calling party the relay'I R is deenergized,

releasing in turn relay T Relay T in releasing its upper, armature removes the ground from the sleeve conductor which is holding relays D Fig. 3, and D (Fig. 4), operated. Relay Ti, in closing its lower con- .tact operates the release magnet 331 to restore placed the receiver on the hook, the release of the connector is revented by slow relay 545 which holds up by its lower winding, in series with the line loop of the called party, the circuit being as follows :-battery, lower winding and armature 520 of relay 545, contact 556 of relay 550, armature 558 and front contact of relay 553, now operated, armature 560 and front contact of slow relay 545, armature and back contact of relay B, through the substation loop returning over armature 561 and back contact of relay B armature 562 and front contact of relay 545, armature 522 and front contact of relay 553, conductor 563, upper armature and back contact of relay 550,

conductor 564, armature 507 and back contact of relay 550, conductor 517, armature 542 and front contact of relay 545 to ground at the armature 525 and back contact of relay 544. Relay 553 is at this time held up from this same ground. When the called party replaces the receiver on the hook, relay 545 is released, and in turn releases relay 553. The release of relay 545 connects ground'through the armature 525 and back contact of relay 544, armature and back contact 542 of relay 545, armature 541 and back contact of relay 550, causing the release magnet ,543 to restore the connector.

lVhen ground potential is removed from conductor 300, the circuit of relay 1) is opened and this relay releases. Relay D completes a circuit from ground through its upper armature, conductor 206, contact 212, right back contact of relay T off-normal contact ON, winding of the release magnet 233 to battery. Magnet 233 releases the selector As the selector switch reaches normal, a circuit is completed from ground, through the contact of D conductor 206, right back contact of relay T lower contacts ON in their normal position, thence through the off-normal contact 133, winding of the release magnet 194 to battery. Magnet 194' energizes and releases the finder switch shown in Fig. 1.

- In case of a busy line, or if the called subscriber is the first to hang up, the releasing operations are the same as those described, except that the removal of ground from the sleeve wire 406 causes the re ease of relays 550 and 545 which results in the closure of the circuit of release magnet 543.

It will be noted that talking conductors 441, 442 of the upper trunk in the even level 444 are multipled byconductors 445, 446 to the talking conductors 431, 432. of the upper trunk in the odd level 430; also that the talking conductors 422, 423 of-the lower trunk in the even level 444 are multipled by conductors 447, 448 to the talking conductors 433, 434 of the lower trunk in the odd level 430. The test terminal 407 of the lower trunk in the even level is not directly connected with the test terminal of the lower trunk in the odd level however as in the case of the talking multiples, but is connected by conductors 406 and 436 through the lower winding of the brush shifting relay B (Fig. 5) as described.

The test terminal 457 would be similarly connected over conductors 443, through a relay corresponding to B of the other connector and conductor 435 to test terminal 449.

It will be understood therefore, that though four sets of terminals are shown at the right of Fig. 4, two trunks 441, 442 and 422, 423 only extend from these sets of terminals. Each of these trunks of course terminates in a connector. Both of these connectors serve the same two hundred line group. Assuming the selector (Fig. 4) takes ten rotary steps,

it will be evident that it will test twenty trunks, two at each step, terminating in twenty connectors, these connectors serving a given group of 200 lines, and that when the seized connector is set the particular line connected to will depend upon which level 444, 430, the connector was seized from, as has been pointed out.

Assume as has been described in detail that the connector has been seized from the lower trunk in the even level 444 and set on a line in the even hundreds. The relay B in this case is inert. Now the trunk terminating in the connector is also multipled to the terminals 433, 434, in the odd level, and the test terminals 407, 436 of these trunks are now connected together through relay 13". Means must be provided to prevent a selector when testing contact 436 from operating relay B of the used connector, since if this relay operates under such conditions it will open the talking circuit of the connection established by this connector.

As pointed out this connector when seized is made busy to selectors from the ground on armature 460 of relay D*, Fig. 4, over the fol-. lowing path: ground, armature 460, conductor 450, armature 412 and front contact of relay B, brush 411 to the multiple 407.

Now, when another selector tests multiple 436to which multiple 407 is connected over the lower windin of brushshifting relay B (Fig. 5), its re a F must operate from the ground applied by the said armature 413 to advance the selector past this trunk. The relay B is made slow to operate in order to take care of this condition and the 'relay' F will get plenty of time to operate from this ground and transmit an impulse to the rotary magnet to step the selector ahead before the relay B can operate.

What is claimed is:

1. In a telephone system; a calling line;

trunk lines; first selector switches; second selector switches accessible via trunk lines over a pair of levels in the first selector switches; connector switches accessible via other trunk lines over a pair of levels in said second selector switches; every selector and connectorswitch having a pair of brush sets,

a magnet for operating said brush sets, and circuits for controlling said magnet; means for causing a first selector to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the seizure of a trunk to a second selector for trans forming the magnet controlling circuits of the first selector into an impulse repeating device; means controlled by the calling line for operating the magnet of said second selector through the medium of the impulse repeating device; means thereafter effective for causing said second selector to test the trunks to the connectors in pairs and to seize an idle one; means determined by the level of the second selector from which said connector trunk is seized for rendering operative the proper connector brush set; and a circuit, including the brush operating magnet of the connector andthe impulse repeating device, controlled by the calling line.

2. In a telephone system; a calling line; a called line trunk lines; first selector switches; second selector switches accessible via other trunk lines over apair of levels in the first selector switches; connector switches accessible via other trunk lines over a pair of levels in said second selector switches; every selector switch having a pair of brush sets, a magnet for operating said brush sets, and circuits for controlling said magnet; every connector switch having a pair of brush sets, magnets for operating said brush sets, and circuits for controlling said magnets; means for causing a first selector to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the seizure of a trunk to a second selector for transforming the magnet controlling circuits of the first selector into-an impulse repeating device; means controlled by the calling line for operating the magnet of said second selector through the medium of the impulse repeating device; means thereafter efiective for causing said second selector to test the trunks to the connectors in pairs and to seize an idle one; means determined by the level of the second selector from "which said connector trunk is seized for rendering operative the proper connector brush set; circuits, including the brush operating magnets of the connector and the impulse repeating device, controlled by the calling line for extending the connector to the called line via one of its brush sets; and means effective after said set of brushes is set for restoring to normal said impulse repeating device'and establishing the talking circuits in said first selector.

3. In a telephone system, the combination of a telephone line,'a' selector therefor having a number of sets of brushes, trunks accessible to each set, means for causing said selector to wipe over and test a number of said trunks simultaneously and to stop when an idle trunk is reached, and means for extending said telephone line to said idle trunk, said means always consisting of a single test rela 4. In a telephone systennthe combination with a telephone line, a selector therefor having a number of sets of brushes, trunks accessible to each set, means for causing said selector to Wipe over and test a pair of said trunks simultaneously and to stop when an idle trunk is reached, means for extending said telephone line'to the idle trunk consisting of a single test relay, means for energizing said relay prior to the testing operation and for connecting the same to one test brush, a circuit for holding'said relay operated if the said brush finds the associated trunk busy, the idlecondition of the other trunk causing the stopping of the selector, the said relay extending said telephone line to said last mentioned trunk.v

5. In a telephone system, the combination with a telephone line, a selector therefor having a number of sets of brushes, trunks accessible toeach set, means for causing said solector to wipe over and test a pair of trunks.

simultaneously and to stop when an idle trunk is reached, means consisting of a single test relayfor extending the telephone line to the idle trunk, a circuit for energizing said relay prior to the testing operation, and

for connecting the same to one test brush,

means for opening said first circuit when the test is made, the idle condition ofboth trunks causing said relay to release and extend the said telephone line to the trunk associated with the test brush to which the relay was connected.

6. In a telephone system, the combination of a telephone line, a selector therefor, having a number of sets of brushes, trunks accessible to each set, means for causing said selector to wipe over and test a pair of trunks simultaneously and to stop when an idle trunk is reached, means consisting of a single test relay for extending the telephone line to the idle trunk, a circuit for energizing said relay prior to the testing operation and for connecting the same to one test brush, means the said line to the said last mentioned trunk, 1

7. In a telephone system, the combination with telephone lines, findersetherefor each having a pair OfSets of talking brushes and test brushes and cooperating terminals, trunk lines, means for causing said brushes to wipe over and test said lines in pairs upon the initiation of a call and to stop the finder when the calling. line is reached, and means for connecting the brush sot engaging the calling line to the associated trunk, said means consisting of a single test relay.

' 8. In a telephone system, the combination with telephone lines, trunk lines, finders therefor each having a pair of setsof brushes, trunk lines, means for testing said lines in pairs upon the initiation of a call and for' connectlng the brush set engaging the calling line to the associated trunk, said means consisting of a brush shifting relay energized prior to the testing operation and connected to the test brush of one set. and held operated by the non-calling one of the pair of lines to connect the brush set engaging the calling line to the said trunk. I

9. In a telephone system; the combination with telephone lines; finders therefor each having a pair of sets of brushes, each brush set comprising talking brushes and a test brush; trunk lines; and means for testing said telephone line in pairs upont-he initiation of a call and for connecting the brush set engaging the talking conductors of the calling line to the seized trunk, said means consisting of a brush shifting relay energized prior to. the testing operation and connected to the test brush of one brush set, said relay being released it the line whose talking conof said brush set is calling, said relay in releasing connecting the trunk via said brush set to the calling line.

10. In a telephone system, the combination withtelephone lines, finders therefor, each having apair of sets of brushes, trunk lines, means for testing said lines in pairs upon the initiation'of a call and for connecting the brush set engaging the calling line to the associated trunlg sa-id means consisting of a brush shifting relay energized prior to the testing operation and connected to the test brush of one set, said relay being held operated by the non-calling one of the pair of lines to which it is connected, and a circuit closed from the other non-calling line and a front contact of said relay to step the finder to the next pair of lines. o

11. In a telephone system, the combination the testing operation with telephone lines, trunk lines, finders therefor each having a pair of sets of brushes, trunk lines, means for testing said lines in pairs upon the initiation of a call and for connecting the brush set engaging the calhng'lme to the associated trunk, said means consisting of a brush shifting relay energized prior to and connected to the test brush of one set and held 0 erated by the non-calling one of the pair of lines to connect the brush set engaging the calling line to the said trunk, and a circuit for independently holding said relay operated.

12. In a telephone system, the combination with telephone lines, trunk lines, finders therefor each having a pair of sets of brushes, trunk lines, means for testing said lines in pairs'upon the initiation of a call and for connecting the brush set engaging the calling line to the associated trunk, said means consisting of a brush shifting relay energized prior to the testing operation and connected to the test brush of one set and held operated by the non-calling one of the pair of lines to connect the brush set engaging the calling line to the said trunk, and a locking circuit for said relay including an off-normal switch of said finder.

13. In a telephone system, trunk circuits, an automatic switching mechanism having both a primary and a secondary movement, automatic switches accessible thereto via said trunk circuits, means for setting the switching mechanism in accordance with its primary movement, means for thereafter initiating its secondary movement for causing said switching mechanism to simultaneously test two trunks and to seize the first idle one, and means thereafter effective for converting said switching mechanism into an impulse repeating device.

14. In a telephone system, trunk circuits, an automatic switch having both a primary and a secondary movement, other automatic switches accessible thereto via said trunk circuits, means for setting the switch first mentioned in accordance with its primary movement, means for thereafter initiating its secondary movement, means effective during its secondary movement for causing said switch to simultaneously test two trunks and to seize the first'idle one, means thereafter effective for converting said first mentioned switch into an impulse repeating device, and means in theswitch associated with the trunk thus seized for operating it in accordance with its primary movement through the medium of said impulse repeating device.

15. In atelephone system; trunk circuits; a switching mechanism having a primary and a secondary movement; a first group of switches accessible thereto via certain of said trunk circuits; means for operating said switching mechanism in accordance with its primary movement; means for thereafter initiating its secondary movement; means effective during its secondary movement for causing said switching mechanism to simul-, taneously test two trunk circuits leading to said switch group and to seize an idle one; means thereafter effective for converting said switching mechanism into an impulse repeating device; a second group of-switches accessible to the seized switch of the first group via other trunk circuits; means for operating the seized switch in accordance with its primary movement through the medium of the impulse repeating device; means thereafter effective for initiating the secondary movement of said switch; means in said switch, eflectivecduring itssecondary movement, for causing it to simultaneously test two trunks leading to said second switch group and to seize the first idle one, whereby said impulse repeating device is connected to the seized switch of the second group; and means for setting the switch last seized through the medium of the impulse repeating device.

16. In a telephone exchange system; a calling line; a called line; groups of auto matic switches, each switch having both a primary and a secondary movement; means, controlled by the calling line, for causing one switch in each group to be set in sequence to build up a connection to the calledline, means in one of the switches in the train, effective during its secondary movement, for causing said switch to simultaneously test two switches of the succeeding switch group and to seize an idle one; means thereafter effective for converting said seized switch into an impulse repeating device; and means, under control of the calling line, for operating said repeating device to set the subsequent switches in the train.

17. In a telephone system; a calling line; a called line; groups of automatic switches, each switch having a primary and a secondary movement; a primary magnet in each switch operable to control the primary movement thereof; means included in the calling line for causing the primary magnet of one switch in each group to be operated in building up a connection to the called line; and means including a relay in one switch of the train, for controlling the primary magnet of its switch, for controlling the sub-sequent secondary movement whereby said switch is caused to simultaneously test two switches of the succeeding switch group and to seize an idle one, and for controlling in turn the operation of the primary magnet of every subsequent switch in the train.

18. In a telephone system; telephone lines; trunk lines; finders associated therewith, each having two sets of brushes, each set comprising talking brushes and a test brush; test terminals, one for each telephone line; means responsive to the initiation of a call on a tele- I phone line for causing a finder to pass over and test the telephone lines in pairs, said means comprising a brush shifting relay energized prior to the testing operation and locked via the test brush of one brush set to the test terminal of one line in each pair passed over, the relay being released if the test brush via which it is locked encounters the test terminal of the calling line, said relay in releasing causing the linking of the trunk and the calling line.

19. In a telephone system; telephone lines; automatic switches; finders, one for each automatic switch, each finder having two sets of brushes, each set including talking brushes and a test brush; test terminals, one for each telephone line; means responsive to the initiation of a call for causing a finder to pass over and test the telephone lines in pairs, said means comprising a brush shifting relay en-.

ergized' prior to the testing operation and locked via the test terminal of one line in each pair passed over, the relay being released if the test brush via which it is locked encounters the test terminal of the calling line, said relay in releasing causing the automatic switch to be placed in operative-relation with the calling line.

20. In a telephone exchange system; a calling line; a called line; groups of automatic switches, each switch having both a primary and secondary movement; means, controlled by the calling line, for causing one switch in eachgroup to be set in sequence to build up a connection to the called line; means in one of the switches in the train, efiective during its secondary movement, for causing said switch to simultaneously test two switches of the succeeding switch group and to seize an idle one; means thereafter effective for converting said seizing switch into an impulse repeating device; means, under control of the calling line, for operating said repeating device to set the subsequent switches in the train; and means, effective after the last switch in the train has been set, for restoring to normal saidimpulse repeating device and establishing the talking circuits in said seizing switch.

" 21. In a telephone exchange system; a calling line; a called line; groups of automatic switches, each switch having both a primary and a secondary movement, and provided with a stepping magnet for controlling the primary movement thereof; means, controlled by the calling line, for causing one switch in each group to be set in sequence to build up a connection to the called line; means in one of the switches in the train,.efl'ective during its secondary movement, for causing said switch to simultaneously test two switches of the succeeding group and to seize an idle one; means efi'ective thereafter for converting said seizing switch into an impulse repeating device; means, including the stepping magnet of each subsequent switch in the train in turn, whereby each subsequent switch is set in sequence under control of the callin line through the medium of said repeating evice;

said repeating device including a relay for controlling the steppin magnets of the subsequent switches, said re ay and each stepping magnet in turn mutually controlling each other; and 'means effective after the last switch in the train has been set, for restorin to normal said impulse repeating device and establishing the talking circuits in said seizing switch.

22. In a telephone system; a calling line; a called line; groups of automatic switches;

each switch having a primary and a secondary movement; means included in said callin line for causing one switch in each group to e set in accordance with its primary movement in building-up a connection to the called line via the switch train; means in one switch of the train eflective during its secondary movement for causing said switch to simultaneously test two switches of the succeeding switch group and to seize anidle one; means responsive to said seizure for converting said switch apparatus into an impulse repeating device; a relay in said repeating device; a stepping magnet in the succeeding switch operable to set said switch in accordance with its primary movement; means, under control of the calling line, for operating said relay and stepping magnet over mutually controlled circuits means in said succeeding switch, effective during its secondary movement, for causing said switch to simultaneously test two switches of the next succeeding switch group and to seize an idle one; a'stepping magnet in the switch last seized operable to set said switch in accordance with its primary movement; means, under the control of the calling line, for operating said relay and the stepping magnet in the switch last seized over mutually controlled circuits; a source of talking battery; and means to restore to normal said impulse repeating device for supplying said talking battery to the calling and called lines.

23. In a telephone system; a calling line; a called line; groups of automatic switches; each switch having a primary and a secondary movement; groups of trunks, there being one trunk per switch; a primary magnet in each switch; means included in said calling line for causing the primary magnet of one switch in each group in turn to be operated in accordance with the primary movement of the. switch in building up a connection to the called line; a relay in one switch of the train; means including said relay for controlling the primary magnet of said switch; means for controlling the secondary movement of said switch whereby it is caused to simultaneously test two'trunks leading to the succeeding switch and to seize an idle one; means including said rela for converting said switch into an impu se repeating device for controlling the primary magnet of each subsequent switch in the train in turn over mutually controlled circuits including said relay and the roper primary magnet; a source of talking attery; and means eflective when the called line is seized for disconnecting said relay from the impulse rcpeating device and for restoring to normal said repeating device for supplying said talking battery to the calling and called lines.

24. In a telephone system; a selector switch having a primary and a secondary movement; trunks accessible to said switch; other automatic switches reached via said trunks; means for setting said selector switch in accordance with its primary movement; means thereafter effective for initiating the secondary movement of the switch and for causing it to. simultaneously test the trunks accessible thereto in pairs and to seize an idle one; means, included in said selector switch, for transforming it into an impulse repeating device means for setting said other switches in sequence through the medium of said impulse repeating device; and means, efl'ective after the setting of the last switch has been completed for restoring to normal said impulse repeating deviceand establishingthe talking circuits in said selector switch.

25. In a telephone exchange system; a calling line; acalled line; groups of automatic switches, each switch having both a primary and a secondary movement. and provided with a stepping magnet; means, controlled by the calling line, for causing one switch in each group to be set in sequence; means in one of the switches in the train, effective during its secondary movement, for causing said switch to simultaneously test two switches in the succeeding switch group and to seize an idle one; means thereafterefl'ective for converting said seizing switch into an impulse repeating device; and means, including the stepping magnet of each subsequent switch in the train in turn, whereby each subsequent switch is set in sequence under control of the calling line, through the medium of said repeating device, to build u a connection to the called line; said repeating device including a relay for controlling the stepping magnets of the subsequent switches, said relay and each stepping magnet in turn mutually cont-rolling each other. a

26. In a telephone system; a calling line; a called line; groups of automatic switches, each switch having a primary and'a secondary movement; means included in said callingline for causing one switch in each group to be set in sequence in accordance with its primary movement, in building up a connection to the called line via the switch train; means in one switch of the train effective during its secondary movement for c using said switch to simultaneously test two switc the succeeding switch group and to seize an idle one; means in said switch responsive to said seizure for converting said switch into an impulse repeating device; a relay in said repeating device; a stepping magnet in the succeeding switch operable to set said switch in accordance with its primary movement; means for operating said relay and stepping magnet over mutually controlled circuits, under the control of the calling line; means in said succeeding switch, effective during its secondary movement, for causing said switch to simultaneously test two switches of the next succeeding switch group and to seize an idle one; a stepping magnet in the switch last seized operable to set said switch in accordance with its primary movement; and means for operating said stepping magnet and the relay in the repeating device over mutually controlled circuits under the control of the calling line. i

27. In a telephone system; a calling line; a called line; groups of automatic switches, each switch having a primary and a secondary movement; a primary magnet in each switch; means included in said calling line for causing the primary magnet of one switch in each group in turn to be operated in ac cordance with the primary movement of the switch in building up a connection to the called line; a relay in one switch of the train; means including said relay for controlling the primar magnet of said switch; means for control ing the secondary movement ,of said switch whereby it is caused to simultaneously test two switches of the succeeding switch and to seize an idle one; and means including said relay for converting said switch into an impulse repeating device for controlling the primary magnet of each subsequent switch in the train, in turn, over mutually controlled circuits including said relay and the proper primary magnet.

28. In a telephone system; a calling line; trunk lines; first selector switches; second selector switches accessible via trunk lines over a pair of levels in the first selector switches; connector switches accessible via other trunk lines over a pair of levels in said second selector switches; every selector and connector switch having a pair of of brush sets, a magnet for operating said brush sets, and circuits for controlling said magnet; means controlled by the calling line for extending said line to a first selector switch; means controlled by the calling line for operating the magnet of said first selector; means thereafter efiective for causing said first selector to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the esot" seizure of a trunk to a second selector for transforming the magnet-controlling circuits of the first selector into an impulse repeating device; means controlled by the called line for operating the magnet of said second selector through the medium of theimpulse repeating device; means thereafter effective for causing said second selector to test the trunks to the connectors in pairs and to seize an idle one; means determined by the level of the second selector from which said connector trunk is seized for rendering operative the pro er connector brush set; and a circuit, inclu 'ng the brush operating magnet of the connector and the impulse repeating device, controlled by the calling line.

29. In a telephone system; a calling line; a called line; first selector switches; line finders; means responsive to the closing of the calling line circuit for causing said line finder to extend said calling line to a first selector switch; second selector switches accessible via trunk lines ovr a pair of levels in the first selector switches; connector switches accessible via other trunk lines over a pair of levels in said second selector switches; every selector switch having a pair of brush sets, a magmet for operating said brush sets, and circuits for controlling said magnet; every connector switch having a pair of brush sets, magnets for operating said brush sets, and circuits for controlling said magnets; means for causing said first selector to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the seizure of a trunk to a second selector for transforming the magnet-controlling circuits of the first selector into an impulse repeating device; means controlled by the called line for operating the magnet of said second selector through the medium of the impulse repeating device; means thereafter effective for causing said second selector to test the trunks to the connectors in pairs and to seize an idle one; means determined by the level of the second selector from which said connector trunk is seized for rendering operative the proper connector brush set; circuits, including the brush setting magnets of the connector and the impulse repeating device, controlled by the calling line for extending the connector to the called line via one of its brush sets; and means, effective after said set of brushes is set, for restoring to normal said impulse repeating device and establishing the talking circuits in said first selector.

30. In a telephone system; a calling line; a called line; first selector switches; line finders; means responsive to the closing of the calling line circuit for causing said line finder to pass over the lines to which-it has access to test them in pairs and to seize the calling -line; means thereafter efiective to extend said calling line via said line finder to a first selector switch; second selector switches accessible via trunk lines over a pair of levels in the first selector switches; connector switches accessiblevia other trunk lines over a pair of levels in said second selector switches; every selector switch having a pair of brush sets, a

magnet for operating said brush sets, and circuits for controlling said magnet; everyconncctor switch having a pair of brush sets magnets for operating said brush sets, an

circuits for controlling said magnets, means for causing said first selector to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the seizure of a trunk to a second selector for transforming the magnet-controlling circuits of the first selector into an impulse repeating device; means controlled b the calling line for operating the magnet 0 said second selector through the medium of the impulse repeating device; means thereafter effective for causing said second selector to test the trunks to the connectors in pairs and to seize an idle one: means determined by the level of the second selector from which said connector trunk is seized for rendering operative the proper conncctor brush set; circuits, including-the brush setting magnets of the connector and the impulse repeating device, controlled by the calling line, for extending the connector to the called line via one of its brush sets; and means, effective after said set of brushes is set, for restoring to normal said impulse repeating device and establishing the talking circuits in said first selector. v

31. In a telephone system: a calling line; first selector switches, line finders individual thereto; means responsive to the closing of the calling line circuit for causing said line finder to pass over the lines to which it has access, to test them in pairs, and to seize'the' calling line whereby said calling line is extended to said first selector switch; second selector switches accessible via trunk lines over a pair of levels in the first selector switches; connector switches accessible via other trunk lines over a pair of levels in said second selector switches; every selector switch having a pair of brush sets, a magnet for operating said brush sets, and circuits for controlling said magnet; every connector switch having a pair of brush sets, magnets for operating said brush sets, and circuits for controlling said magnets, means for causing said first selcctor'to test the trunks to the second selectors in pairs and to seize an idle one; means responsive to the seizure of a trunk to a second selector for transforming the magnet-controlling circuits of the first selector into an impulse repeating device; means controlled by the called line for operating the magnet of said second selector through the medium of the impulse repeating device; means thereafter effective for causing said 

